Can you attack through full cover?

An eldritch knight wants to attack a guard behind a wall. Before, he casts scrying and thus can see the target and where they are behind the wall.

How this should be resolved?

Is he unable to attack through the wall? Or it depends on the material of the wall? Or it counts as attacking a location? How should advantage/disadvantage be applied to this?

I really want this to work because having a knight in full plated armor greet the enemy through the wall with a giant axe seem awesome, but my DM insists on giving me ruling support.